Perinatal depression is a major public health problem, affecting 15% of women during pregnancy through the postpartum period, with adverse consequences for the mother, the fetus, the infant, and the family. Despite increasing evidence of the importance of this critical risk interval, little research has investigated the effects of depression treatment during pregnancy on infant outcomes. The purpose of this study is to test the feasibility, acceptability, and effectiveness of a new intervention, Interpersonal psychotherapy for the mother-infant dyad (IPT-Dyad). This intervention begins during pregnancy and continues with the mother and infant until one year postpartum. The investigators hypothesize that IPT-Dyad will be better than treatment as usual in reducing depressive symptoms, improving psychosocial functioning,increasing parenting self-efficacy, improving infant emotional development, and enhancing mother-infant relationship quality.